Although time is always our scarcest resource, I've enjoyed helping other business leaders or emerging executives by sharing my experiences, through serving on Boards or through mentorship roles. When its with highly engaged people, I feel I get more learning from the sessions than what I give out.
One of the things I've learned in this process is that its important that we frame our advice and feedback as sharing of experiences, and not being directive and prescriptive about what the management team (in the case of Boards) or Mentees need to do. There is an implicit 'power-distance' hierarchy between the Board and management or between Mentor and Mentee, and if we are too directive, then it is hard to not do what's being 'told'. And we lack the day-to-day context to really be able to know exactly what needs to be done. Instead, by sharing our experiences, we enrich the recipient with new perspectives and allow them to self-discover their own decisions and have a stronger sense of ownership to carry it out.
From my experience, the best engagements come from sessions that are prepared ahead of time. Management or Mentees should take the time to craft a 1-2 page document that summarises the key issues: context or situation, options, and challenges faced. This will help focus the meetings on joint problem solving and experience sharing. The most effective of these meetings are when 75% of air-time comes from Board members probing and sharing experiences and joint problem solving. Meetings that have been less productive (but sadly more common) are when Management spends 75% of the time presenting detailed 50-100 slides that provide background information (that could have been read beforehand) and Board members only ask a few questions or point to a few errors on the slides.